Surgical drain

ABSTRACT

In a surgical drain system formed with two or more branches, exudate flow from a patient&#39;s wound is directed between two branches with the respective filling and emptying times determined in order to identify the presence of a blockage in the drain.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of and priority to European PatentApplication Serial No. 17305602.9 filed May 23, 2017, the disclosure ofthe above-identified application is hereby incorporated by reference inits entirety.

BACKGROUND

This invention relates to a surgical drain for use in medicalapplications and a method.

SUMMARY

A number of surgical procedures require a patient to be provided with asurgical/medical drain to aid recovery. Surgical drains are medicaldevices used to provide a connection to a body cavity to allow fluids toflow out of the patient to a collection vessel. The drained fluids caninclude pus, blood or other fluids which gather at a wound site andcould become a focus for infection or retained blood complications. Thedrained fluid is sometimes referred to as “exudate”. The drain remainsin place until the exudate flow has stopped, or has become less than apredetermined volume, for example, 25ml per day. In order to assist thehealing process, it is also known to gradually withdraw the drain fromthe wound by 2cm per day, thus facilitating healing whilst maintainingthe draining of the wound.

The fluid may be drawn from the wound by gravity or assisted by use ofan active surgical drain utilising a vacuum pump.

Surgical drains may be made from a variety of materials to cater for arange of procedures. Typically, these are PVC, rubber or silicone formedinto a tube of a diameter of 2 to 6 mm and may range in length from 50to 100 cm.

The form of the exudate provides a useful indication of the healingprocess. The exudate is monitored as to its colour and consistency sincethat may indicate a change in the patient's condition. For example, asudden change in the colour of the exudate to be more “bloody” and moreprofuse may indicate a haemorrhage. A change from thin and pink to thickand brown could indicate faecal material leaking into the wound and acolour change to green may indicate infection and the potential forsepsis.

Monitoring the exudate is therefore very important but it will also beappreciated that monitoring by nursing staff is time consuming and,between inspections, it is possible for conditions to arise which arenot discovered for many hours until the next scheduled inspection takesplace. This delay may have serious consequences for the patient, asremedial treatment to correct a post-operative condition, such as aninfection, is delayed.

Another issue experienced, is that the exudate flow may drop for reasonsnot associated with there being less material in the wound to bedrained. For example, the drain may become clogged, and the flowreduced, even though the wound itself still needs draining. This canlead to the drain being removed too early from the patient in the falsebelief that the wound is healing.

It has been proposed to provide drains with sensors to monitor theexudate flow. However, such sensors are sometimes inaccurate as a resultbecoming “fouled” by materials in the exudate or by blockage of thedrain.

The present invention arose in an attempt by the inventors' to alleviatethe problems associated with blockage or obstruction of a surgicaldrain.

According to the invention there is provided, a surgical/medical draincomprising at least a first branch and a second branch; a flowcontroller operative to in use control flow through the branches andmeans to monitor the rate of flow therethrough; a comparator to comparethe respective rates of flow through the first and the second branch andto provide an output representative thereof

By providing at least a first and second branch and controlling the flowtherethrough, the flows may be compared to determine the presence of ablockage downstream of the branches. In particular, if a first branch isfilling at a rate faster than the other branch is emptying then thedownstream section is blocked. The rate of difference between fillingand emptying of the branches will depend on the severity of theblockage. More than one branch is required but more than two branches,three or more, may also be utilised to provide some element ofredundancy, for example, to cater for one branch or its associatedsensors and flow control failing. Two branches are provided in thedescribed embodiment.

Preferably, an alarm device is provided which is responsive to theoutput to provide an alarm. The alarm may be an audible alarm, a visualalarm or combination of the two which may be presented to a user of thesystem or provided to another system.

Preferably, respective input and output valves are provided to controlthe flow through the branch under the control of the flow controller.

In the described embodiment, which is preferred, the valves controlinput and output from the branches. But other means are envisioned. Forexample, the valve action may be provided by a magneto-strictive elementoperable to reduce the diameter of the branch. Such an element may beprovided about a wall defining the branch to constrict the branch orintegrally formed within the branch. In the described embodiment, aninlet valve is opened and an outlet valve is closed to allow the branchto fill. The other branch is opened at the same time to allow it toempty. This is done by closing the inlet valve to prevent exudateflowing into that branch and the outlet valve is opened to allow thebranch to empty into the next section of the drain. In the describedembodiment, which is preferred, the valves open and close in a binaryfully open fully closed manner but in alternative embodiments the valvesmay open proportionally, that is to say, partly opened and partlyclosed.

There will be many ways in which the state of fill of the branches maybe sensed. The sensors may be resistive sensors, capacitive sensors,reactive sensors, or optical or other sensors or combinations of these.The sensors may be formed on arrays attached to an outer or innersurface of the branches. The sensors may also be integrally formed withthe branch by fabrication and deposition techniques. Preferably, thesensors comprise level sensors within the branches to provide an outputindicative of the level of exudate within the branch. For certainsensors such as optical sensors the branch may be made transparent toallow the sensing of the level from a position exterior of the branch.

In order to determine the exudate flow conditions, preferably, the drainfurther comprises logic means to determine an alarm condition when oneof the branches fills more quickly than the other empties. This may beformed from discrete logic devices or application specific integratedcircuits, ASICs, or by provision of a suitably programmed microprocessorconfigured to follow a software program provided as a set of machinecode language instructions held in memory.

The program may be provided in preloaded read only memory (ROM) ordownloadable from a network or storage device such as a USB or disc. Inthe described embodiment, a number of processing functions are describedas separate blocks but it will be appreciated by the person skilled inthe art that these may be provided on one or more processors. That is tosay, one processor may be programmed to provide more than one of theblocks of functionality.

In the described embodiment, the branches are described as “tanks”. Theyare broader than the remaining sections of the drain in order toaccommodate a plurality of level sensors and to provide a larger volumeto accept the exudate flow but need not be so. That is to say, the tanksmay have the nominally same diameter as the adjacent part of the drain.The tanks may be provided joined or formed together or as separatecomponents.

Preferably, the branches or tanks are of a known ratio of volumes but,most preferably, the tanks are nominally identical volume. This ispreferred as it will simplify the processing in determine the respectiverates of filling and emptying.

One end of the drain will be configured to facilitate insertion into apatient and the other end may be configured for connection to areceptacle for the drained fluids. A vacuum may be applied to thereceptacle to encourage the exudate flow along the drain.

Advantageously, additional sensors may be provided to monitor the flowfrom the patient and at intermediate positions before the branches ofthe drain. This will enable the flow to be monitored at those positionsto determine blockages prior to the branches or tanks. In the describedembodiment the additional sensors are provided at that part of the drainto be inserted into the patient and at a position intermediate that partand the branches. This will allow the inflow from the patient to bemonitored and to be compared to the flow present at the intermediatepart. This may be used to determine a blockage being present before thebranches.

The invention provides in a further aspect a method of determining thepresence of a blockage in a surgical drain in accordance with the firstaspect of the invention comprising the steps of, directing an exudateflow away from a first branch to a second branch in the drain to fillthe second branch, directing an exudate flow from the first branch to anoutput from the drain to empty that branch, comparing the rate offilling of the second branch with the rate of emptying of the firstbranch to determine a blockage condition.

Preferably, the method further comprises the step of providing an alarmwhen a blockage is determined. The step of directing flow includesopening inlet and outlet valves controlling the flow within respectivebranches. Then the rate of filling and emptying is determined by readinglevel sensors determining the level of exudate in respective branchesfor a given time interval.

A data carrier such as a computer disc, memory stick or memory card maystore a set of computer implementable instructions for carrying out themethod. This may be used to program the system to perform the method byconnection via a suitable port such as a USB port or from a drive orover a network.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments of the invention will now be described withreference to the drawings of which:

FIG. 1 shows a schematic view of a drain system in accordance with anembodiment of the invention inserted into a patient having a woundrequiring draining;

FIG. 2 shows in greater detail a schematic cross-sectional view of afirst part of the drain system shown in FIG. 1 with further detail of asensor arrangement;

FIG. 3 shows in greater detail a schematic cross-sectional view of anintermediate part of the drain system shown in FIG. 1 with furtherdetail of a sensor arrangement;

FIGS. 4a and 5 show schematic cross-sectional views of branches formedby tanks of the drain system as seen in FIG. 1 with respective flowcontrol valves for controlling the flow of exudate into and out of thetanks;

FIG. 4b shows a perspective view of the tanks; and

FIGS. 6 and 7 are explanatory diagrams showing the steps performed bythe system to determine the presence of a blockage.

DETAILED DESCRIPTION OF EMBODIMENTS

As is shown schematically in FIG. 1, a drain system 1 in accordance withan embodiment of the invention comprises three distinct parts, A, B andC. Part A is that part of the drain which interfaces with the patientbody by insertion into the body. This part may be several millimetres toa few centimetres long. Part B is the length of drain tube intermediatethe patient's body and a flow meter provided as part C. The drain tube 2is of a familiar type being formed from a medical grade siliconematerial having a diameter of 5 mm. Exudate is conducted from thepatient by the drain to pass through part A, B and then through part Cto be deposited into a collection vessel or bag 2.

Part A is shown in greater detail in FIG. 2. It includes a number ofsensors SA1 to SAn located within a section of the drain tube 2. In thefigure, the drain tube containing the sensors is shown having a greaterdiameter than the inlet and outlet part of the tube but it will beappreciated that the diameter of the drain tube may, in alternativeembodiments, be substantially the same. The sensors are connected to asensor bus 3 and from there to a processor.

Part B also includes a similar arrangement of sensors SB1 to SBn againconnected to a sensor bus 3 and to the processor.

The outputs from the sensors from parts A and B can be used to determineif there is a blockage along these sections of the drain by comparisonof the respective flow rates as will be appreciated by a person skilledin the art without further elaboration.

Part C is formed of two or more tanks arranged in parallel and a valvearrangement for controlling the filling of the tanks as is shown inFIGS. 4a, 4b , and 5. They form branches in the drain though which theexudate may flow. The tanks 40, 41 are formed of plastics material tohave matching volumes. In this particular embodiment, the tanks have avolume of 2ml although other volumes may be used or ratios of volumes.This particular volume is useful as it allows a measurement to be takenof the exudate level every 15 minutes for a flow rate of 100ml per 24hour period with each measurement being of approximately 1 ml per 15minute period.

Located at the entrance and exit of each tank is an inlet valve 42, 43and an outlet valve 44, 45. The valves 42 to 45 are motorised valvesoperated by a control system 46. The control system 46 is microprocessorbased operating in accordance with machine executable code stored inlocal memory. Its structure and method of operation will be laterdescribed.

Each of the tanks 40, 41 is provided with a plurality of sensors 40 aand 41 a mounted to the internal wall as shown in FIG. 1. Each sensorcan provide an output of the level of exudate within the tank as theexudate builds up (level increases). The sensors are connected to thecontrol system 46 over the sensor bus 3.

The flow control system 46 monitors each of the sensors and determinesif there is an abrupt change in flow conditions. If such is detected, adownstream flow obstruction check process is performed. In this, thevalves 42 to 45 are selectively opened and closed in a synchronisedmanner under the control of the flow control system 46 to determine thepresence of an obstruction. This will be more fully described laterafter an overview of the system is given.

Reverting now to FIG. 1, the control system 46 includes a processor 50,a comparator 51, a flow controller 52, a memory 53 and an alarm 54. Thememory 53 is provided as a combination of Read Only Memory (ROM) andRandom Access Memory (RAM) to hold data and a program as a set ofexecutable code instructions to govern the system operation under theprocessor 50.

The comparator 51 is connected to the sensor bus 3. It reads each of thesensors and performs a comparison to determine the respective flow ratesthroughout the parts A, B and C, and to deduce therefrom if there areany blockages. In the event that a blockage is determined then an outputis provided to the processor 50 which instructs the alarm 54 to give anaudible and visual alarm signal to warn nursing staff.

The flow controller 52 is connected to a valve control bus 55 to providecontrol output to each of the valves 42 to 45. The bus also allowsstatus information for the valves to be passed back to the flowcontroller. The flow controller 52 operates as instructed by theprocessor 50 to control the selection of the tanks to fill or empty inaccordance with the predetermined scheme as referred to earlier byopening and closing valves in a synchronised manner. That is to say,valves 42 and 44 are operated at the same time such that when valve 42is opened valve 44 is instructed to close and when valve 42 isinstructed to close, valve 44 is instructed to open. Similarly, whenvalve 43 is instructed to open, valve 45 is instructed to close and whenvalve 43 is instructed to close, valve 45 is instructed to open. To filla tank, the inlet valve is opened and the outlet valve is closed, thatis to say, valves 42, 43 are opened and valves 44 and 45 are closed whentheir respective tanks are to be filled. To empty a tank, the valves 42,43 are closed and valves 44, 45 are opened.

In normal operation the tanks are opened and allowed to fill or closedand allowed to empty in an alternating manner. That is to say, when tank40 is to be filled tank 41 is to be emptied and vice versa.

In a first phase, tank 40 is filled. To do this valve 45 is opened,valve 44 is closed and valve 42 opened and valve 43 closed. This isdepicted in FIG. 4a . This causes tank 40 to fill and tank 41 to empty.To allow this to occur a vent “V” is located in an upper position in thedividing wall “W” between the tanks to allow for air to flow between onetank and the other that would otherwise be trapped as is shown in FIG. 4b.

In a second phase, as depicted in FIG. 5, tank 40 is full, and is to beemptied, and tank 41 is empty and is to be filled. The control system 46signals valve 45 to close and valve 44 to open. At the same time, valve42 is instructed to close and valve 43 to open.

During this process, the control system monitors the signals of the tanksensors. In the event that the tanks do not empty or empty more slowlythan the tank being filled then the control system 46 determines thatthere is an obstruction downstream of the tanks.

The way in which the system operates will now be described withreference to FIGS. 6 and 7.

In a first step 60, the system initialises. This is carried out when thedrain is inserted into the patient and the system is switched on by themedical staff In this step the system “boots up” and performs checks onthe various sensors and valves in the system to ensure that they areoperational. The status of the system and its components may beindicated on a display to the staff.

In the next step 61, the tank to be filled and the tank to be emptiedare selected. In this case tank 40 is selected to be filled first andthe tank 41 selected to be emptied. Accordingly, the flow controller 52is instructed by the processor 50 to set the valves to the correctstates. Valve 42 is opened to the forward part of the drain, valve 44 isclosed and valve 43 is closed to the forward part of the drain (butopened to atmosphere) and valve 45 opened. Tank 40 then fills as theexudate is drained and tank 41 empties.

In step 62, a period of time is allowed to elapse to allow the exudateflow to be established.

In step 63, the fill level of the tank being filled is determined by thecomparator 51 polling the sensors within the tank. The sensor determinesthe level of the exudate in the tank. This is compared with apredetermined threshold held in memory in step 64 and the comparisonrepeated. If the threshold is reached, then the tank is considered to befull and the process progresses to step 65.

In step 65 the tanks are switched to the alternative state. That is tosay, the tank being filled is selected to be emptied and the tank beingemptied is selected to be filled. Following the above, tank 40 isselected to be emptied and tank 41 is selected to be filled. To do this,flow controller 52 is instructed by the processor 50 to switch the valvestates. That is to say, valve 42 is closed to the section B (but openedto atmosphere), valve 44 is opened to allow the exudate to flow out ofthe tank 40. The valve 43 of tank 41 is opened to section B (and closedto atmosphere) and valve 45 is closed. Tank 41 then proceeds to fill.

The tank fill and emptying rates are then determined and stored inmemory 53 in steps 66 and 67 by the processor 50 instructing thecomparator 51 to provide the outputs of the tank sensors. In this, theexudate levels are checked in the tanks at respective time intervalsdetermined by a system clock (not shown). Thus, the stored states at theparticular time intervals provide a rate of filling or emptying of thetanks.

In a process 70 shown in FIG. 7, the processor 50 accesses the storeddata from memory 53 in step 71. It then compares the fill levels at thetime intervals in step 71, and in step 72, determines the rate offilling and the rate of emptying of the tanks. The average difference inthe rate is determined in step 73.

In step 74, the difference in the rate is compared with a predeterminedthreshold value held in memory 53. If the threshold is not exceeded thenthe processor accesses the data from memory for the next tank stateswitching and repeats steps 71 to 74. If the threshold is exceeded, thenan alarm is issued in step 75 by suitable instruction from the processor50 to the alarm device 54.

The medical staff will then be aware of the blockage and may takeremedial action by replacing the drain, or parts of it, as required toclear or remove the blockage.

As will be appreciated there will be a number of variations andcombinations of features disclosed in the application which will fallwithin the scope of the recited claims.

What is claimed is:
 1. A surgical drain for, in use, conducting exudatefrom a patient wound,comprising: a tube having an inlet portion, anoutlet portion, a first branch and a second branch, the tube defining afirst flow path including the inlet portion, the first branch and theoutlet portion, and the tube defining a second flow path including theinlet portion, the second branch and the outlet portion, wherein thesecond branch is outside of the first flow path; a flow controllerconfigured to, in use, control flow of the exudate through the firstbranch and the second branch and means to monitor a rate of flowtherethrough; and a comparator to compare respective rates of flowthrough the first branch and the second branch and to provide an outputrepresentative thereof.
 2. The surgical drain of claim 1, furthercomprising an alarm device responsive to the output.
 3. The surgicaldrain of claim 1, wherein first and second branches are provided withrespective input and output valves to control flow therethrough underthe control of the flow controller.
 4. The surgical drain of claim 1,further comprising level sensors within the first and second branches toprovide an output indicative of a level of exudate within the first andsecond branches.
 5. The surgical drain of claim 1, further comprisinglogic means to determine an alarm condition when one of the first branchor the second branch fills more quickly than the other of the firstbranch or second branch empties.
 6. The surgical drain of claim 1,wherein the first and second branches comprise tanks.
 7. The surgicaldrain of claim 6, wherein each tank has a nominally identical volume. 8.The surgical drain of claim 1, wherein the inlet portion of the tubeincludes at least one exudate sensor for determining an exudate flowtherethrough, and wherein the inlet portion includes a portionconfigured for insertion, in use, into a patient.
 9. The surgical drainof claim 8, further comprising an intermediate portion connecting theinlet portion to the first and second branches.
 10. The surgical drainof claim 9, further comprising sensors located in the intermediateportion to determine an exudate flow therethrough.
 11. The surgicaldrain of claim 1, further including a plurality of valves disposed inmechanical cooperation with the tube and configured to direct the flowof exudate through one of the first flow path or the second flow path ata particular time.
 12. The surgical drain of claim 1, further includinga plurality of valves disposed in mechanical cooperation with the tubeand configured to direct the flow of exudate through the first flow pathand the second flow path in an alternating manner.
 13. The surgicaldrain of claim 1, wherein exudate configured to flow in the first flowpath bypasses the second branch of the tube.
 14. The surgical drain ofclaim 13, wherein exudate configured to flow in the second flow pathbypasses the first branch of the tube.
 15. The surgical drain of claim1, wherein the first branch and the second branch are arranged inparallel.
 16. The surgical drain of claim 1, wherein the tube dividesinto the first branch and the second branch and then reunites into theoutlet portion.